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Los Angeles (CNN)A Nissan Sentra belonging to the gunman who opened fire in a murder-suicide at UCLA was found parked Friday in a residential area of Culver City, police said.

It's a major clue in the investigation of Mainak Sarkar, the former UCLA grad student who apparently killed his estranged wife in Minnesota before driving cross country to Los Angeles to kill a former professor and then himself, Capt. Robert Hayes of the Los Angeles Police Department robbery-homicide unit said Friday night.

One development didn't involve the car. Preliminary ballistics testing shows the same weapon was used to kill Sarkar's wife in Minnesota and the UCLA professor in his campus office, said Matt Blake, the LAPD chief of detectives.

Officers found several cans of gasoline and a loaded pistol inside the car, Hayes said at a news briefing.

The gasoline cans probably didn't have any "nefarious" purposes, Hayes said. Sarkar may have wanted to avoid detection on the cross-country drive and stayed away from gas stations, he said.

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'No trigger event'

Why was the car in Culver City? Sarkar previously lived there while attending UCLA, Hayes said, and may have simply parked in a known neighborhood

Officers found a bus transfer in in Sarkar's pocket, Hayes said, leading officers to think he took a familiar bus to campus, carrying his weapon in a backpack.

But nobody knows what motivated Sarkar to kill his wife, Ashley Hasti, and then a former professor of his, William Klug, Hayes said.

"No trigger event has been found," he said.

Denver on Tuesday

Police are working on a timeline. A police automatic license plate reader in Denver noticed Sarkar's vehicle on Tuesday. He probably arrived in Los Angeles on Wednesday because that's the date on the bus transfer, Hayes said.

"We have not found any place he stayed along the way," Hayes said. "I'm sure it was a straight -through drive."

Sarkar, 38, stormed into one-time adviser Klug's office on the California campus Wednesday, shooting him dead and putting the campus on lockdown for hours. Sarkar killed himself before police could arrest him.

Investigators found a note, according to LAPD Chief Charlie Beck, asking for the finder of the note to check on his cat in Minnesota.

Police searched Sarkar's residence there and found a protective vest, ammunition, some medications and computers, Hayes said.

They also discovered a "kill list" naming Klug, wife Hasti and a second professor authorities are not naming. That professor was off-campus at the time and was not harmed.

'Funniest person I knew'

Police went to Hasti's in nearby Brooklyn Park, Minnesota early Thursday morning and found her dead of multiple gunshot wounds. Minnesota authorities think she'd been dead several days, Hayes said.

Ashley Hasti's sister, Alex Hasti wrote on Facebook: "Ashley Hasti ... was the smartest, coolest, and funniest person I knew. She could do anything she dreamed of whether it was studying abroad in four different countries, acting in school plays, trying stand up comedy and improv, and becoming a doctor. Unfortunately, she won't get to see that last dream come true as her life was cut short much too soon by her estranged husband."

Hasti and Sarkar married June 14, 2011, Hennepin County officials have said. It was unclear whether they were married at the time of their deaths.

Police say Mainak Sarker was the shooter in a murder-suicide Wednesday at UCLA.

"Everybody tries to look for a reason for this. Well, first of all, there is no good reason for this," Beck told the station. "This is a mental issue, mental derangement, but it was tied to a dispute over intellectual property."

Sarkar felt the professor he killed had released information "that harmed him," he told KTLA. "UCLA says this is absolutely not true. This is the workings of his imagination."

Klug fondly remembered

It had been several years since Sarkar was a student at UCLA. He graduated in 2013 with a Ph.D. in engineering.

Klug's wife, Mary Elise Klug, issued a statement on Thursday thanking the public for its support and requesting privacy.

"During this extremely difficult time for our family, we are grateful for the tremendous outpouring of support. This is an indescribable loss. Bill was so much more than my soulmate. I will miss him every day for the rest of my life. Knowing that so many others share our family's sorrow has provided a measure of comfort," she said.